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The AAT prime focus and CCD observer (1997)

Tags: AAT, David Malin, astrophotography, photography, prime focus

When the Anglo-Australian Telescope was used to take conventional photographs the observer rode in the prime focus 'cage' at the top end of the telescope where light from the primary mirror is brought to a focus. This is shown in the previous picture. However, since the mid 1990s, astronomical images began to be acquired with increasingly sophisticated electronic detectors known a CCDs (charge-coupled devices), and these have now completely replaced traditional photography.

These are larger and much more elaborate versions of the light detectors used in most digital cameras. In practice they are now operated remotely from the telescope control room, or even from another location entirely, but as they were being developed the observer was required to change the filter and to make other adjustments necessary for observing. This picture was made in 1997, and it shows the observer holding a filter wheel. However, now there is now no need for the observer to ride inside the 'cage' at all. Not only is there no need — there is no room (see AAT 4d).

Credit: David Malin

© Australian Astronomical Observatory